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What type of screw is this?


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I'm working on a vintage Citizen watch and came across these screws that are used on the barrel, ratchet and crown wheel. They each have three slots in them but don't seem to take a screwdriver.
What type of screw is this and what is the correct method for removing them?

citizen_screw_heads.JPG

citizen_crown_gear.jpg

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That is a left hand thread screw. A normal screwdriver should work . Had one on the barrel on the citizen 1803 i serviced recently. Which makes it hard to remove as the barrel wind when you remove it . I hold a finger on the ratchet wheel. 

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I don't know and don't quite understand the power flow of this, is it an alarm mov.t?

I can't understand neither why a left threaded screw would be used on a wheel turning clockwise. Of the two meshing above, one certainly is.

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10 minutes ago, jdm said:

I don't know and don't quite understand the power flow of this, is it an alarm mov.t?

I can't understand neither why a left threaded screw would be used on a wheel turning clockwise. Of the two meshing above, one certainly is.

Not sure why citizen has done this. But sure is left hand threads on all of this screws. It's an alarm movement. 

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